Background Helicobacter pylori infection and atrophic gastritis (AG) are markedly more prevalent in Japan than in other industrialized countries, however, the reasons for such a high prevalence are not fully understood.

To add to information on H. pylori infection and its association with AG, the authors studied Japanese living in less developed countries.

Methods Cross-sectional surveys were conducted of randomly selected Japanese residents aged 40-59 years in Sao Paulo, Brazil and Lima, Peru.

Serum IgG antibody to H. pylori and pepsinogen I (PGI) and II (PGII) were measured as markers of AG.

Results The prevalence of H.

Pylori infection was similar in both populations, 77% (95% CI : 70-83) in Sao Paulo and 75% (95% CI : 65-82) in Lima, and was within the range of five populations in Japan from our previous study.

However, the prevalence of AG, defined by PGI<70 ng/ml and PGI/PGII<3.0 was more prevalent among Japanese in Sao Paulo (39% [95% CI : 32-47]), than Japanese in Lima (18% [95% CI : 12-27]). This difference was not explained by sex, age, generation or H. pylori infection.

Conclusions Helicobacter pylori infection among Japanese in less developed countries was similar to Japanese in Japan, although prevalence of AG varied.

Factors other than H. pylori infection are important in the development of AG among Japanese.